Theoretical Analysis of Lowest Limits of NOx Formation of Methane-Air Mixtures

NO_x emission has been limited in many countries because of its adverse impact on environment. Many new strategies and technologies are developed to restrain the NO_x formation in industrial furnaces and power systems. However it is impossible to reduce the NO_x infinitely. There should be a critical value that NO_x emission can´t be reduced anymore. The present paper will estimate the critical value of NO_x formation of methane-air mixture in theory. Under the lowest combustion temperature, the NO_x formation should be reduced to a minimum level. In addition, it is found that the correlation between residence time and NO_x formation presents almost a linear relation. In the industrial furnace, it is estimated that the critical value of NO_x formation is in the order of 10^-9 ppm.